The most common situation you’ll run into in WatchKit where you need to involve the parent app is performing a task that you can’t perform on the watch. Perhaps you need to make a network connection; perform computationally intensive image rendering that would take much longer than the watch app will be active; or access a system framework that’s unavailable from WatchKit, such as HealthKit. WKInterfaceController has a class method built exactly for these needs: openParentApplication(_:reply:). Pass in a Dictionary and a closure to be executed when the task is done, and your iPhone app takes over. Let’s implement this in the TapALap app to save workout data to HealthKit.